The present invention relates generally to pipe and ductwork for commercial applications, and, more particularly, to a lightweight corrosion-resistant and flame-retardant conduit for fluid (liquid and air) conveyance.
Non-pressurized fluid conduits have been developed for countless applications over the years as the mechanical, structural, and materials arts have progressed in response to industrial growth and technological change. Most materials have been selected based upon both their suitability for a particular application, and their relative costs when compared to other suitable materials. For example, galvanized steel pipe and concrete have been the materials of choice for many years for subsurface, non-pressurized drainage and conveyance. While relatively inexpensive and especially suitable to these applications because of their corrosion-resistance, these materials are extremely heavy and bulky, thus requiring installation by mechanical contractors using heavy equipment. For instance, a 10 inch, Schedule 40 galvanized steel pipe will weight approximately 40 pounds per linear foot, and individual pipe sections are typically more than 10 feet long. The resulting labor costs are high and the time required to complete the tedious installation is therefore extensive. The added precautions necessary to safeguard workers from injury when handling such massive structures also increase costs and assembly time.
Above surface fluid conduits have also been problematic. Air circulating systems, including air ducts, supply relatively low pressure forced air heating and cooling in residential, commercial, and industrial applications. In commercial and industrial applications, the air ducts, which are conventionally formed of heavy sheet metal, must be suspended from structural load-bearing members using supporting hardware, or xe2x80x9changers.xe2x80x9d While sheet metal is lighter than concrete or galvanized steel, suspended installation is also laborious and requires special hoists or other lifting devices to position the duct sections and hold them in place while they are interconnected and supported. Further, overhead insulated ductwork has its own special problems, especially with leaking condensation from overhead chilled water piping saturating the fiberglass, or other insulation material surrounding the ductwork. Such leakage also produces chemical reactions of the binder that holds the fiberglass together to produce phenol and formaldehyde, both occupationally undesirable. While lighter, composite, insulated conduit systems would be desirable, none have been known that provide acceptable corrosion resistance or ability to meet recognized flame-retardance testing, or are safe to occupants during known or anticipated operating conditions or failures.
In addition to installing the subsurface or above surface conduits described above, fluid conduits normally must be insulated and sealed to minimize thermal losses, conceal hot surfaces, or block moisture penetration. Typically, an insulation contractor performs this necessary second step. Lastly, the insulated conduits are covered with a jacket or vapor barrier. The total installation process must therefore be accomplished in the field in three steps. Unfortunately, poor materials, less than ideal field conditions, and workmanship often lead to hazardous conditions, undue maintenance, and premature replacement of conduits.
The present invention relates, in part, to a lightweight, corrosion-resistant and flame-retardant conduit that addresses the problems described above for non-pressurized fluid conveyance.
In a preferred embodiment, a lightweight corrosion-resistant conduit for fluid conveyance comprises an outer conduit portion and an inner conduit portion. The outer conduit portion is formed of a rigid foam material and has an outer surface and an inner surface, and first and second ends. The inner conduit portion is formed of the same foam material and has an outer surface and an inner surface and first and second ends. The outer surface of the inner conduit portion substantially conforms to the inner surface of the outer conduit portion. The inner and outer conduit portions are aligned and adhered together such that the first end of the inner conduit portion protrudes outwardly beyond the first end of the outer conduit portion to form a male end, and the second end of the inner conduit portion is recessed into the second end of the outer conduit portion to form a female end.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments when considered in conjunction with the drawings. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.